DESCRIPTION: The overall aim of this project is to elucidate the neural circuit mechanisms underlying the brain's ability to control its own sensory input. To address this issue, large number of single neurons (up to 128) will be recorded simultaneously through multi-electrode arrays implanted in multiple processing levels of the trigeminal somatosensory system of awake rates, during immobility and will performing exploratory wwhisking movements. Simultaneous recordings have recently been obtained in the trigeminal ganglion (Vg), principal (PrV) and spinal SpV) trigeminal nuclei, ventral posteromedial (VPM) thalamus, and somatosensory (SI) cortex. Aim #1 is to continue current studies of spatiotemporally distributed "shifting" receptive fields in neurons in the VPM and SI, which appear to be learned through motor experience. Aim #2 is to determine whether active whisker movement produces and "efference copy" which modulates sensory transmission according to the phase and "motor intention" of the movement. Aim #3 is to record from the same neurons in rats trained to discriminate among several tactile objects using active whisking.